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A Vision for Intelligent Transportation Systems and Traffic Safety in the
Era of Big Data
Satish Ukkusuri, Professor of Civil Engineering, Purdue University
Wenbo Zhang, PhD Candidate, Purdue University
ABSTRACT
With rapid economic growth in developing countries, vehicle ownership and trip
making has increased resulting in more congestion and safety issues. The
transportation infrastructure and management, however, lag behind relatively. This
leads to deteriorated quality of life (congestion and emissions) and traffic crashes.
More importantly, the growing inequalities between access to transportation and
the interactions between motorized vehicles and non-motorized transportation
modes on roads. This is compounded by the heterogeneity of vehicle class (e.g.
motorbikes, three wheelers etc) in developing countries. Due to the lack of enough
traffic barricades and smart traffic controls, the mixed traffic increases the traffic
crash frequency and results in increased risk for non-motorized transportation
modes.
This paper will introduce new ideas and strategies, such as vision zero program,
for reducing the overall crashes in a country. Then the paper reviews the new
trends in speed limit, especially variable speed limit, physical isolations.
Furthermore, some special policies, developed for non-motorized transportation
modes, especially for motorized/electrical bicycles, to reduce traffic crashes, are
discussed. Second, to optimize the management of traffic at the network level and
at intersections smart intersection control strategies will be presented. Data to
support the traffic management from cameras, GPS equipped vehicles and social
media will be discussed. A demonstration of the different tools developed by Dr.
Ukkusuri’s lab will be shown. Finally, combining with the new trends in
connected vehicles and autonomous vehicles, the potential benefits of these
revolutionary transportation tools, especially in traffic safety, are summarized.
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INTRODUCTION
According to the report released by World Health Organization (WHO), road
traffic injuries has become the eighth leading cause of death all over the world,
especially for the youth between 15 and 29. (World Health Organization, 2013a)
Each year, approximately 1.24 million people die on roads and another 20 to 50
million sustain non-fatal injuries. Although no overall reduction in the number of
people died from traffic crashes, considering the context of 15% increase in the
number of registered vehicles, most countries have made progresses in reducing
the related deaths and also show that this reduction is possible. However, the
report from the WHO also shows that the total number of road traffic deaths
remains unacceptably high and can be reduced further, especially in low- and
middle- income countries, such as Vietnam. Figure 1 shows changes in the road
traffic deaths rate in Vietnam and 10 other countries, including a few developed
countries and some countries in Southeast Asia. From the figure, the road traffic
death per 100,000 populations has a decreasing trend in Vietnam in recent years.
The average level, however, is still significantly higher than most countries that
have an average level of less than 10 deaths per 100,000 populations. Thus, the
reduction in road traffic deaths is still possible in Vietnam and more efforts should
be made for this field.
Figure 1. The changes in road traffic deaths rate in Vietnam and 10 other countries
The report from WHO also discussed the traffic laws or policies that address five
main risk factors, including speed, drunk-driving, helmets, seat-belts, and child
restraints. Only 28 countries that cover 7% of the world’s population have
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adequate laws or policies. (World Health Organization, 2013b) For most countries
with corresponding laws or policies, the enforcement that is critical to success is
inadequate. In addition, over a third of road traffic deaths in low- and middleincome countries are related to pedestrians and cyclists. However, less than 35%
of those countries have policies in place to protect these road users. For example,
Vietnam is with national speed limit, drink-driving law, motorcycle helmet law,
seat-belt law, and mobile phones prohibition while driving. Especially for
motorcycle helmet law, this has pushed the helmet-wearing rate from below 30%
to over 95%. This big progress didn’t change the safety of vulnerable groups
significantly, as shown in Figure 2-a. And less effective enforcement should still
be improved, as shown in Figure 2-b. there is also a pressing need to introduce
new techniques or ideas to solve current road-crash crisis in the country.
(a) road traffic crash distribution among vehicle types
(b) causes of road traffic crashes
Figure 2 Road traffic crash analysis in Vietnam
Different from traditional 5E’s (i.e. Engineering, Education, Enforcement,
Emergency, and Evaluation) approach to safety, more and more transportation
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system designers are trying to explore solutions through technological
improvements, such as Intelligent Transportation System (ITS). It has been
verified that related ITS technologies can improve transportation safety and
mobility, reduce environmental impacts, and enhance productivity through
incorporating advanced information and communication techniques into
transportation system. The United States Department of Transportation has long
been a leader and strong supporter of ITS and also issues a strategic plan in the
next five years, i.e. realizing connected vehicle implementation and advancing
automation. (Barbaresso et al, 2014) Furthermore, according to the Grand View
Research Inc., an institution on market research and consulting, the global market
for ITS is expected to reach USD 38.68 billion by 2020. ITS aids in reducing
incidents such as road accidents and boost safety, which is estimated to positively
impact demand over the next six years.
This paper tries to integrate the ITS and road traffic safety. Besides some new
ideas in traffic safety in the second part, the paper will introduce some advanced
approaches to a safer highway and intersection in the third and fourth part
respectively. Moreover, some new and automated data collection techniques under
this era of big data are introduced to assist in developing smart and safer highways.
Finally, future directions in ITS, such as connected vehicles and autonomous
vehicles, are discussed to approach road traffic safety.
VISION ZERO PROGRAM
Vision zero is a bill on traffic safety, passed by the Swedish Parliament in 997. It
states that vision zero means that eventually no one will be killed or seriously
injured within the road transport system and that the transport system designers –
including members of the motor vehicle industry, road traffic planners, road safety
engineers, police, health professionals, educators, and road users- have a shared
responsibility to ensure that the transportation system protects all travelers, even
when they make mistakes or are at fault. (Fahlquist, 2006; Tingvall, 1997) This
idea is also called “Scandinavian model” of road safety thinking. The new
paradigm is significantly different from traditional traffic safety philosophy
(McAndrews, 2013; World Health Organization, 2004):
1. Traffic injuries are preventable, not accidental;
2. In addition to road user, all stakeholders- transportation, health, and so onare responsible for road safety and should share responsibility for it;
3. Transportation systems should be designed to be tolerant of road users’
errors, and road users who make errors should not die or be seriously
injured because of them;
4. Safe transportation systems should be designed around the human body’s
limited tolerance for harmful kinetic energy;
5. Road safety is a social equity issue, not just an engineering and design
problem;
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6. Assistance from high-income to low-income countries should target local
conditions and needs; and
7. Safety interventions should be based on local knowledge, not only the
application of professional guidelines.
The distribution of responsibility introduced by Vision Zero could be an efficient
tool to use to get closer to achieving the goal of substantially reducing road traffic
deaths. However, this paradigm does suggest a code of ethics for road safety
experts and not include ways in which experts can be held directly accountable for
traffic crashes in a consistent or coherent way. In order to implement this
ambitious and far-reaching goal and have long-lasting effects, it is very important
and necessary that the industry does its part and the crucial question is how this
can be achieved and whether legal sanctions have to be attached to the current
distribution of moral responsibility for it to be truly efficient.
Based on the current most cost-effective measures, some studies also tried to
propose measures under Vision Zero in five main areas, including speed
regulation, application of ITS, vehicle modification, road system modification,
new safety regulations for road users, and strict enforcement. (Elvik, 1999)
Although these measures haven’t met the underlying idea of Vision Zero to
stimulate the development of new safety measures, it is a good initial step to
implement Vision Zero. Some US major cities, such as New York City (NYC),
San Francisco, and Boston, have started to implement Vision Zero. Taking NYC
as example, the city council passed 11 bills and 6 resolutions to implement Vision
Zero Action Plan across many city departments in 2013, including: strict
enforcement for speeding, failure to yield to pedestrians, and dangerous driving; a
campaign in the state legislature to allow the city to lower speed limits to 25mph;
safety improvements such as traffic calming, speed cameras, and slow zones on
streets; stricter scrutiny of taxi drivers’ safety records; and street safety curriculum
in schools. (Walljasper, 2015) Till 2014, the maximum speed limit of almost 90%
of streets in NYC has been reduced from 30mph to 25mph. Meanwhile, the
speeding tickets increased by 40%. Figure 3 shows the system with statistics of
fatalities and injuries in August 2015, as a part of NYC vision zero action plan.
The results are also promising that the NYC had an historic low for pedestrian
fatalities in 2014.
Different from the Vision Zero to reduce road traffic deaths and serious injuries,
some new concepts of motorcyclist safety polices go further and is more focused
on accident prevention than death and injury reduction. With better understanding
of motorcycles and motorcyclists, the riders’ organization in western countries
also proposed their safety improvements within five aspects, i.e.
human/motorcyclists, vehicle/motorcycles, transportation environment and
infrastructure, and social impacts. The detail policy mainly includes licensing,
training crash avoidance skills, education on hazard awareness and panic
management, personal protective equipment, motorcycle modification and
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intelligent equipment, road hazards and maintenance, motorist awareness, rider
peer pressure, and public attitude.
Figure 3 The system under NYC Vision Zero Action Plan
SAFER AND SMART HIGHWAYS
Variable speed limit
Speed limit is a widely used strategy to implement Vision Zero. Typically,
depending on temporal dimension, the speed limit control strategy can be
classified into two categories: traditional static speed limit and variable speed limit
(VSL), as shown in Figure 4. Traditional static speed limit has been used for
decades and shows fixed maximum speed through a traffic sign at a fixed segment.
However, with the introduction of ITS, more and more engineers have been
focusing on VSL that can change speed limit accordingly and dynamically.
Because the speed limit is determined on the basis of prevailing road traffic and
environmental conditions, VSL can directly and efficiently influence the road
safety. Moreover, VSL is often based on the principle of speed homogenization
over the road segment, which can further improve road capacity and reduce speed
variability. Previous studies found that VSL reduces variance in speed, leads to
fewer collisions, improve safety by about 50% and mobility by about 30%, and
also reduces exhaust emissions by 2-8%. (Grumert and Tapani, 2012; Islam et al,
2013)
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(a) traditional static
(b) variable
Figure 4 The speed limit control strategy (sources: USDOT)
Except for the benefits of VSL, researchers also focused on how to implement
VSL and develop optimal scheme. Islam et al (2013) collected data from an urban
freeway corridor in Canada and tested the sensitivity of the VSL update frequency
and the safety constraints for the VSL strategy based on micro simulation platform,
VISSIM. To approach the best scenario in terms of safety and mobility, the VSL
update frequency of 5 min and a maximum speed difference of 10 km/h between
successive time steps yields the best performances. Zhu and Ukkusuri (2014) also
proposed a novel method to determine optimal real time speed limit, which can
account for uncertain traffic demand and supply in a stochastic traffic network.
This study, different from traditional safety research, was based on stochastic
network perspective and assigned time dependent speed limit for each link in this
network. With the simulation on the Sioux Falls network, the VSL could reduce
travel time and emissions by 18% and 20% respectively. Grumert and Tapani
(2012) also discussed the cooperative VSL system that covered multi segments. In
this cooperative VSL system, vehicles could communicate with roadside unit and
receive updated speed limits before reaching a point where they can actually read
the speed limit signs. The speed limits is given to the vehicles at predefined points
in time and are depending on the vehicle speed, speed limits given from the
roadside unit located in front of the vehicles, and distance between the vehicles
and roadside unit. Thus, vehicles adapted their speed earlier and continuously,
which could reduce the very high acceleration and deceleration rates and then
improve safety, mobility, and emission.
Moveable or Active Physical Isolation
Traffic calming is the combination of mainly physical measures that reduce the
negative effects of motor vehicle use, alter driver behaviors, and improve
conditions for non-motorized street users. (Lockwood, 1997) This has been
verified as one efficient way to protect non-motorized road traffics, such as
pedestrian, motorcyclists, bicyclists, and transit users. The physical isolation, such
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as known as traffic barriers, guardrails, crash barriers, and traffic marking, is one
of widely used traffic calming techniques. It can keep vehicles within their
roadway and prevent vehicles from colliding with dangerous obstacles, opposing
traffic, and vulnerable travelers, as shown in Figure 5-a. Moreover, it can also be
used to protect vulnerable areas, such as school area and pedestrian zones from
errant vehicles, as shown in Figure 5-b. The drawbacks of traffic barriers are also
obvious, one of which is not moveable and cannot adapt traffic flow. An
innovative moveable barrier technology has been invented to create safe and
dynamic highways that offer real time roadway reconfiguration while maintaining
positive barrier protection between lanes. The system uses a wall of interlocked 1meter barriers that can be lifted and repositioned by transfer machine to create
isolated zones or lanes for special purposes. The transfer machine can move with a
speed of 11km/h. This system has been implemented on UK highway A21.
(a) median barriers
(b) crash barriers for vulnerable travelers
Figure 5 Traffic barriers on urban streets
Figure 6 Moveable barrier (Sources: Lindsay Inc.)
The above physical isolation techniques are efficient during daytime. The
visibility of these techniques, however, will be a problem in nights. Furthermore,
this problem is more serious in Vietnam. The roads are poorly lit and are with few
road signs. Buses and trucks often travel at high speed with bright lights; and some
motor vehicles don’t use any lights and may stop in road segments without
illumination. The additional light and traffic signs on road are needed in Vietnam.
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The LED active light-emitting road traffic signs and barriers may be a potential
solution. These signs and barriers can absorb and store solar energy through panel
and battery and emit light actively in the dark, as shown in Figure 5 and 7. Besides
these active light-emitting road traffic signs and barriers, some more smart traffic
signs, markings, and barriers has been proposed, including glowing lines,
interactive light, and Van Gogh bicycle path. All the three new things absorb solar
energy during the day and emit lights in the dark. The glowing lines are mainly
designed to show borders of each lane, as shown in Figure 8-a&b; the interactive
light system is installed on median barriers and only turns on when traffic
approaches in the dark, as shown in Figure 8-c; and the Van Gogh bicycle path is
developed for bicyclists and makes up of thousands of sparkling stones that can be
charged and emit light, as shown in Figure 8-d. These new innovations are seen as
safe, sustainable, and cost-saving alternative to conventional lighting for dark
roads.
Figure 7 LED active light-emitting road traffic signs
SAFER AND SMART INTERSECTIONS
Different from the physical isolation that separates traffic spatially on highway
segments, traffic signals that separate traffics temporally are widely used at
intersections. The traffic signals can reduce the traffic conflict greatly, which can
improve traffic safety at intersections. There are three main types of traffic signal
control strategies in practice, including the basic operation, the time-of-day
operation, and the adaptive operation. The signal timing schemes for the first two
types are programmed based on anticipated demand or anticipated demand at
different time periods. The last one, however, requires vehicle detection and
dynamically adjusts signal timing schemes based on current or historical demand,
as shown in Figure 9-a. With the proliferation of communication and information
techniques, Dresner and Stone (2008) proposed a multiagent systems approach to
intersection management called autonomous intersection management that can
utilize the full capacity of autonomous driving systems. This system describes a
First Come, First Served policy for directing vehicles through an intersection.
Moreover, all vehicles and infrastructures are connected and can communicate
with each other; and no traditional traffic signals are installed at intersections, as
shown in Figure 9-b. In simulation, this approach has been shown to yield
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significant improvements in intersection performance over conventional
intersection control strategies, such as traffic signals and stop signs.
(a) Glowing lines on roads
(b) Glowing lines from driver’s view
(c) Interactive light system
(d) Van Gogh bicycle path
Figure 8 Innovations on smart highways
(Sources: Studio Roosegaarde & Heijmans)
(a) adaptive intersection
(b) autonomous intersection
Figure 9 Smart intersections (Sources: SCOOT, USDOT)
The Split Cycle Offset Optimization Technique (SCOOT) is a tool to implement
adaptive system that responds automatically to fluctuations in traffic flow through
the use of on-street detectors embedded in the urban roads. It has proven to be a
world leader in urban traffic control that typically reduces traffic delay by an
average of 20%. Furthermore, it also contains functions of bus priority, traffic
gating, incident detection, on-line saturation occupancy measurement, and vehicle
emission estimates. This tool has been installed successfully in several cities, such
as Beijing, London, Toronto, Southampton, and York. Dr. Ukkusuri also explored
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different types of traffic control strategies extensively. Ukkusuri et al (2010)
proposed a method to develop optimal and robust signal timing scheme
considering network wide impacts, traffic dynamics, and uncertainty in the OD
demand. Except for traffic signal control for a single intersection, Zhu et al (2015)
proposed a machine learning method to inference exactly the best joint actions for
all the coordinated intersections. Abdul Aziz et al (2012) made a further
discussion on adaptive signal control and developed a new method to account for
neighborhood congestion information sharing. Thus, in new methods, local traffic
information, as well as neighborhood traffic information, are considered. Zhu and
Ukkusuri (2015) also discussed the novel methods for autonomous intersection
management accounting for traffic dynamics and connected vehicle environment
in the context of system optimum network model. Another study by Abdul Azizi
and Ukkusuri (2014) focused on individuals in terms of stopped delay at
signalized intersections for the entire trip of a user and proposed a new control
strategy that can yield benefits from connected vehicle environment and user
perspectives.
DATA SUPPORT
ITS varies in techniques applied, from introduced techniques such as VSL to more
advanced applications such as connected vehicles and autonomous vehicles.
Additionally, predictive techniques are being developed to allow advanced
modeling and comparison with historical baseline data. Smart decisions are made
and distributed based on modeling, data, and communication techniques. Among
these components, the data collection is an initial but also important step to
approach ITS. For example, VSL needs input of link traffic state; and adaptive
intersection needs input of queue length and neighborhood congestion information.
Various data needs can also be met by various data collection techniques, such as
floating vehicle data, sensing techniques, inductive loop detector, video vehicle
detection, Bluetooth detection, and online tools.
Floating vehicle data collection, also called probe vehicle data collection, is a set
of methods for obtaining travel time and speed data for vehicles traveling along
roads. With the proliferation of location techniques, GPS and smartphones are
equipped within vehicles and provide vehicle position information, as shown in
Figure 10-a. Those readings from vehicles are used to estimate traffic states. Zhan
et al (2013) used large-scale taxi GPS data in New York City to estimate urban
link travel time. Known as non-intrusive method of traffic detection, video vehicle
detection needs cameras, typically mounted on poles or structures above or
adjacent to the lanes, and processors that analyze the changing characteristics of
the video image as vehicle pass. The typical output of video detection system is
speed, volume, occupancy, gaps, and headway, as well as stopped vehicle
detection and wrong way vehicle alarms. Zhan et al (2015) estimated the real-time
queue length based on license plate recognition data from video vehicle detection,
as shown in Figure 10-b. Inductive loops, Bluetooth, and sensing detections,
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shown in Figure 10-c, d and e, are also accurate and inexpensive way to measure
traffic state. Inductive loops are placed in a roadbed to detect vehicles as they pass
through the loop’s magnetic field. Bluetooth is a wireless standard used to
communicate between electronic devices. Bluetooth road sensors, installed at
roadside, can detect Bluetooth MAC address from Bluetooth devices in passing
vehicles. Interconnecting those Bluetooth road sensors can estimate link traffic
states. Similar as Bluetooth, Radio Frequency Identification is one of sensing
techniques and can identify passing vehicles through communication signals and
receiving sensors. Sometimes, online resources are also available for traffic
management, such as Google maps and traffic. In the project of “An agent based
model for the adaptive traffic signal systems”, Dr. Ukkusuri collected traffic data
from Google Maps and estimate link traffic state, as shown in Figure 10-f.
(a) Taxi GPS data in New York City
(c) Inductive loop detector
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(b) Video Camera in Beijing
(d) Bluetooth detection
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(e) Sensing technique of RFID
(f) Online tool of traffic state
Figure 10 Data collection techniques
(Sources: Dr. Ukkusuri’s group, USDOT, and Libelium Inc.)
FUTURE DIRECTIONS
ITS is a set of tools that facilitates a connected, integrated, and automated
transportation system that is information-intensive to better serve the interests of
users and be responsive to the needs of travelers and system operators. It
integrates advanced communications-based information and electronic
technologies into the transportation infrastructure and vehicles. The USDOT, as a
national and even worldwide leader in ITS program, has issued the priorities that
guide the development to harness the personal involvement in near future.
(Barbaresso, 2014) These priorities reflect the needs of stakeholders, including not
only research but also the deployment and implementation of specific technologies.
The first priority of realizing connected vehicle implementation builds on
substantial progress in recent years around design, testing, and planning for
connected vehicles to be deployed across the nations. The second priority of
advancing automation allows the ITS program to delve into this innovative and
cutting-edge field to research, develop, and adopt automation-related techniques as
they emerge.
Different connected vehicle test beds that can offer supporting vehicles,
infrastructure, and equipment to serve the needs of public- and private- sector
testing and certification activities in real world have been created and operating
for several years in four different states, i.e. Michigan, Virginia, California, and
Florida. From the test results, the connected vehicle system have proven to
potentially reduce 81% of all-vehicle target crashes, 83% of all light-vehicle target
crashes, and 72% of all heavy-truck target crashes annually. (RITA, 2014) The
industry also developed different prototypes of autonomous vehicles, such as
Google Self-Driving Car, as shown in Figure 11. The prototypes have been
allowed to take public road testing in California, Michigan, Florida, Nevada, and
Texas. As of July 2015, all 23 Google Self-Driving Car involved in 14 minor
traffic accidents with a total vehicle travelled miles of more than 2 million miles.
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Furthermore, in all cases the vehicle itself was not at fault. The Google has
planned to release the self-driving car model for general public from 2017 to 2020.
Figure 11 The prototype of Google Self-Driving Car (Sources: Google)
SUMMARY
In this new century, the philosophy of traffic safety improvements has changed to
a shared responsibility. All stakeholders are involved in this campaign to reduce
road traffic deaths and injuries. Besides the ideas, the tools and techniques that are
used for traffic safety with the proliferation of communication techniques,
information techniques, and intelligent transportation system. This study also
introduced some new trends in the convergence of intelligent transportation
system and traffic safety. At this great changing world, as well as
transportation system, this is also a valued opportunity for
developing countries, such as Vietnam, to improve current
transportation system and reduce relatively higher traffic crash
rates.
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